Motor with cooled rotor

ABSTRACT

A fan includes an air movement implement including a blade and a motor that drives the air movement implement. The motor includes a rotor that includes an internal diameter heat exchanger and a heat pipe having a first end and a second end, the first end in thermal contact with the internal diameter heat exchanger and the second end in thermal contact with the blade.

BACKGROUND OF THE INVENTION

The present invention is related to motors and, in particular, toreducing the temperature variations experienced by a rotor of a motor.

In many different applications, a motor or other machine that includes arotor that can be placed in systems where it experiences a wide range oftemperatures. For example, an induction motor can be used to drive animpeller that draws air through a heat exchanger in an aircraft. Thecombination of the motor and the impeller is sometimes referred to as aram air fan. While the aircraft is on the ground, outside air is drawnby the ram air fan through the heat exchanger. The air is used to carryheat away from the heat exchanger. Internal portions of the ram air fanare cooled by cooling air that is diverted around the heat exchanger.When the aircraft is in flight, the cooling air is significantly colderthan when it is on the ground. As such, the internal portions of themotor (e.g., the rotor) can experience wide-ranging temperature cyclesthat can result in shortened lifecycles for the rotor.

BRIEF DESCRIPTION OF THE INVENTION

According to one embodiment, a fan that includes an air movementimplement including a blade and a motor that drives the air movementimplement is disclosed. The motor in this embodiment includes a rotorthat includes an internal diameter heat exchanger and a heat pipe havinga first end and a second end, the first end in thermal contact with theinternal diameter heat exchanger and the second end in thermal contactwith the blade.

According to another embodiment, a system that includes an air intake, aheat exchanger coupled to the air intake, an air output coupled to theair heat exchanger, and a fan disposed within the air output that causesair to be drawn in the air intake, through the heat exchanger andexpelled through the air output is disclosed. The fan includes an airmovement implement including a blade and a motor that drives the airmovement implement. The motor includes a rotor that includes an internaldiameter heat exchanger and a heat pipe having a first end and a secondend, the first end in thermal contact with the internal diameter heatexchanger and the second end in thermal contact with the blade.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 is a block diagram illustrating a system in which embodiments ofthe present invention can be implemented;

FIG. 2 is cut-away view of a fan according to one embodiment of thepresent invention;

FIG. 3 is a cross-section of an inner diameter heat exchanger;

FIG. 4 is a graph showing simulated temperature variations for a rotoraccording to the prior art and one embodiment of the present invention;and

FIG. 5 is a cut-away side view of a heat pipe according to oneembodiment of the present invention coupled between an inner diameterheat exchanger and an air movement implement.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a system 100 in which embodiments of the presentinvention may be implemented. The system 100 can be part of an aircraftor any other type of device that can cause the system 100 to be moved ina forward direction. Embodiments of the present invention are directedto a motor 114 that can be used in the system 100. According to oneembodiment, the motor 114 can includes a heat pipe that is used to coolor heat the rotor thereof. In one embodiment, the heat pipe causes therange of a rotor temperature cycle to be reduced as compared to motorsthat do not include a heat pipe.

In FIG. 1, the motor 114 is part of a fan 115 that includes an airmovement implement such as a fan blade or impeller generally shown byelement 116. The motor 114 can be an induction motor in one embodimentbut it shall be understood that the motor 114 could be any type ofelectric motor including, for example, a synchronous motor, a DC motoror a slip-ring AC motor to name but a few. In FIG. 1, the fan 115 isarranged downstream of a heat exchanger 106. The terms upstream anddownstream refer to the direction of travel of a substance (e.g., air)through a system. In particular, a position is upstream of anotherposition if it is closer to the entry to the system than the otherposition. For example, in FIG. 1, assuming that air travels in thedirection shown by arrows A, the heat exchanger 106 is upstream of thefan 115. Further, and in the same vein, the fan 115 is downstream ofheat exchanger 106.

In operation, a heat source 104 is provided from which heat is drawn. Acooling fluid circulates through the heat source 104 and is heatedtherein. The heated fluid is provided through output connection 108 tothe heat exchanger 106. The fluid is cooled as it passes through theheat exchanger 106 and is returned through input connection 110 to theheat source 104 where it can again be used to remove heat from it. Inone embodiment, the heat source 104 includes some or all of theelectronics that operate in an aircraft. It shall be understood,however, that the heat source 104 can be any device or system thatgenerates heat and the heat can be carried from it by means other than afluid.

In FIG. 1, the fan 115 causes input air (illustrated by arrow A) to bedrawn into an input portion 102, through the heat exchanger 106, andthrough an output portion 112 where it is expelled back into theatmosphere as output air (illustrated by arrow B). A cooling duct 118 iscoupled to the input portion 102 such that at least a portion of airdrawn into the input portion 102 is diverted to the motor 114 before theair is heated in the heat exchanger 106. Such air shall be referred toherein as “cooling air” and is illustrated by arrow C.

In operation, while the system 100 is at rest (e.g., an aircraft is onthe ground) the fan 115 is required to draw in input air A. In such acase, the input air A is at a temperature generally in the 0 to 120degrees F. (−17 to 40 degrees C.) range while the output air B is about200 degrees F. (93.3 degrees C.). In such a case, the rotor of motor 114is at a temperature of about 190 degrees F. (87.7 degrees C.). When thesystem 100 is motion (e.g., the aircraft is cruising), the motion of thesystem 100 is all that is need to cause input air A to pass through theheat exchanger 106. In such a case, the motor 114 can be turned off. Themotor 114, however, is still cooled with cooling air C. In suchinstances, the cooling air C is in the range of about the −15 degrees F.(−26.1 degrees C.). The motor housing is heated by the output air B (atabout 200 degrees F. (93.3 degrees C.)). The heating of the motorhousing can heat the rotor to about −10 degrees F. (−23.3 degrees C.).Given the above example, it can readily realized the rotor of motor 114can experience a 200 degree (93.3 degrees C.) or more temperaturevariation each time the system starts and stops moving.

FIG. 2 shows a cut-away side view of fan 115 according to oneembodiment. The fan 115 includes air movement implement 116 (e.g., fanor impeller blade) that is coupled to and driven by motor 114. The motor114 includes an outer shell 200 that surrounds a rotor 203 and a stator208. The rotor 203 includes, in this embodiment, a tie rod 204 coupledto and surrounded by an inner diameter heat exchanger 206. In the casewhere the motor 114 is an induction motor, the rotor 203 can include oneor windings 205 disposed between the inner diameter heat exchanger 206and the stator 208. As is known in the art, the rotor 203 is coupled toand provides a driving force to air movement implement 116 by a shaft220. According to one embodiment, a heat pipe 202 is coupled to the airmovement implement 116 and the inner diameter heat exchanger 206. Asillustrated, the heat pipe 202 is within the shaft 220 but the relativelocations could be varied based on how the shaft 220 is coupled to therotor 203.

FIG. 3 is a cross-section of the rotor 203 taken along lines A-A. Therotor 203 includes the tie rod 204 surrounded by the inner diameter heatexchanger 206. In this embodiment, the inner diameter heat exchanger 206includes an outer shell 302 that defines an outer perimeter thereof andan inner layer 304. One or more fins 306 extend radially between theinner layer 304 and the outer shell 302. The fins 306 define one or moreair channels 308 through which cooling air can pass.

Referring again to FIG. 2, the cooling air C received via cooling duct118 (FIG. 1) can travel through several different paths. For instance, aportion of the cooling air C illustrated as C_(r) can pass through theinner diameter heat exchanger 206. This air serves to generally cool therotor 203. The rotor 203 can also be cooled by a portion of the coolingair C illustrated as C_(r-s) that passes between the rotor 203 and thestator 208 as well as portion C_(s) that passes between the stator 208and the outer shell 200.

The temperature of the rotor 203 will first be explained assuming thatthe heat pipe 202 is omitted and then explained with the heat pipe 202included. In the following explanation it shall be assumed that the fan115 is arranged in a system as illustrated in FIG. 1 and that the systemis part of an aircraft. It shall be understood the fan 115 need not bedisposed in any particular system.

While on the ground, the cooling air C can have a maximum temperature ofabout 130 degrees F. (54.4 degrees C.) and the output air B has amaximum temperature of about 210 degrees F. (98.8 degrees C.). In such acase, the rotor 203 can have a temperature that is about 190 degrees F.(87.7 degrees C.). When the aircraft is in flight, the motor 114 can beturned off. The motor 114, however, still receives cooling air C and thecooling air C is now much colder (in the range of about −10 degrees F.(−23.3 degrees C.)) than when the aircraft was on the ground. In flight,the output air B can warm the outer shell 200 and, to some extent, thestator 208. The rotor 203, however, becomes much colder due to thecooling air C as described above.

FIG. 4 graphically shows simulations of the temperature of the rotor 203as the aircraft is one the ground, in flight, and lands again. Trace 402represents this cycle for the configuration that does not include a heatpipe according to the present invention. Peaks 404 and 406 represent therotor temperature when the aircraft is on the ground and valley 408represents the rotor temperature when the aircraft is in-flight. Asdescribed above, the rotor temperature 402 can vary by around 200degrees F. (93.3 degrees C.) in such a case.

In contrast, trace 410 illustrates the rotor temperature for the samecycle when the heat pipe 202 is added. In general, the heat pipe 202lowers the ground rotor temperature (peak 412) because it allows some ofthe heat to be dissipated through the air movement implement 116.Likewise, the heat pipe 202 can allow heat from the air movement deviceto be transferred to the rotor 203 when the aircraft is in flight and,thereby, raise the in-flight rotor temperature (valley 414). In oneembodiment, only the valley 414 is raised and peak 412 is at about thesame level as the peaks 404, 406.

Referring again to FIG. 2, the heat pipe 202 is illustrated as beingsolid. It shall be understood that in another embodiment, the heat pipecan include an inner cavity formed therein. In either case, the heatpipe 202 can be arranged such that it contacts an end of the innerdiameter heat exchanger 206 and provides a thermal pathway between itand the air movement implement 116.

FIG. 5 shows a detail in cross-section of the heat pipe 202. The heatpipe 202 is in thermal contact with an end 502 of the inner diameterheat exchanger 206 and the air movement implement 116. In FIG. 5, whileon the ground, heat is received from the rotor windings (not shown) asindicated by arrows D. This heat is dissipated by the passage of rotorcooling air C_(r). The heat pipe 202 further dissipates the heat. Inparticular, the heat pipe 202 can provide a thermal pathway to the airmovement implement 116 such that heat (shown by arrows E) can travel outblades 504 of the air movement implement 116.

The heat pipe 202 can be formed of two or more different portions. Asillustrated, the heat pipe 202 includes an inner shell 510, ends 512 andouter shell 514. In one embodiment, the ends 512 and outer shell 514 areformed from a single piece. In one embodiment, the inner shell 510 isformed of a material with a lower thermal conductivity than one or bothof the outer shell 514 and the ends 512. The inner shell 510 can beformed of copper, aluminum, ULTEM or any other suitable plastic materialand one or both of outer shell 514 and the ends 512 can be formed ofcopper or aluminum.

In one embodiment, the heat pipe 202 includes a cavity 505 formedbetween the inner and outer shells 510, 514. The cavity 504 can have awidth w that decreases as the distance from the internal diameter heatexchanger 206 increases. In one embodiment, the inner shell 510 issubstantially cylindrical and has a constant thickness while the outershell 514 has thickness that varies such that the width w varies asdescribed above.

In one embodiment, the cavity 505 can be filled with a fluid. In oneembodiment, the fluid is one of methanol or ammonia. It shall beunderstood that the fluid should remain in the liquid state at thecoldest expected temperature to which it will be exposed. In oneembodiment, the inner shell 510, the ends 512 and the outer shell 514are crimped together. In another, they are ultrasonically weldedtogether.

For ease of explanation, the cavity 505 shall be described as havingnarrow end 530 and wide end 532. The width w is largest at the wide end532 and smallest at the narrow end 530. In one embodiment, the narrowend 530 is located at or near the air movement implement 116 and thewide end 532 abuts the inner diameter heat exchanger 206. The innerdiameter ID of the heat pipe 202 is less than the outer diameter OD ofthe inner diameter heat exchanger 206 in one embodiment.

In one embodiment, the fluid can aid in dissipating heat from the rotorwhile the system in which the motor is placed is stationary (i.e., theaircraft is on the ground). In particular, heat from the inner diameterheat exchanger 206 can cause the fluid to convert to a vapor or gas. Dueto the latent heat of fusion, this change of state can dissipate heat inand of itself. The vapor/gas expands and travels towards the narrow end530 as indicated by arrows. As the vapor/gas reaches the narrow end 530,its heat can be transferred to the air movement implement 116 and bledoff by output air B through blades 504. As the vapor/gas loses its heat,it returns to the liquid phase. The rotation of the air movementimplement 116 and, thus, the heat pipe 202, causes the fluid to trackthe outer shell 514 and travel back towards the wide end 532 asindicated by arrows G where the process can be repeated.

When the system 100 in which the motor 114 is in motion, the rotorcooling air C_(r) can be much colder than when the system 100 wasstationary as described above. In such a case, the heat pipe 202 itselfand the fluid can provide a path for heat from the output air B totravel from the blades 504 back into the inner diameter heat exchanger206 and, consequently, reduce the cooling effect to the rotor coolingair C_(r).

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

The invention claimed is:
 1. A system comprising: an air intake; a firstheat exchanger coupled to the air intake; an air output coupled to thefirst heat exchanger; and a fan disposed within the air output thatcauses air to be drawn in the air intake, through the heat exchanger andexpelled through the air output, the fan including: an air movementimplement including a blade; and a motor that drives the air movementimplement and includes: a rotor that includes an internal diameter heatexchanger; a heat pipe having a first end and a second end, the firstend extending from and in thermal contact with the internal diameterheat exchanger and the second end in thermal contact with the blade, theheat pipe having an inner diameter that defines an internal passagewayfluidly coupled to receive air from the internal diameter heatexchanger; a cooling duct coupled between the air intake and the motorthat provides air that has not passed through the first heat exchangerto the motor, wherein the passageway is fluidly coupled to the coolingduct.